On the existence of two states in liquid water [pdf]
polymer.bu.edu
polymer.bu.edu
https://johncarlosbaez.wordpress.com/2013/11/29/water/
And these things have a very strong temperature dependence. I wonder if it has anything to do with the current discussion.
"This raises the question of whether temperature-driven structural changes in water affect biological macromolecules in aqueous solutions and in particular in proteins... It was found that the temperature stability range of the protein is confined to the reversible interval 45–65°C. ... In all cases the critical temperature of the protein denaturation is very close to the crossover temperature T* observed in all the properties of liquid water reviewed in this work."
This is probably why sous vide temperature is around 60C.
The more interesting thing this finding has to offer is just understanding at a finer detail how proteins interact with water at all, and if there are any properties specific to each state. There might even be cool things like proteins that switch function given the water phase transition. You might find this sort of thing in chaperones related to heat shock for example.
But why are sauna temperatures above this, being in the range of 70C-90C?
Being submerged into a 90 degree water bath will probably rapidly hideously wound you and/or kill you.
They show two graphs of protein denaturation curves showing maximum rate change in 50-65 degree range, and a curve of a different protein's hydration shell density changing. At the very least, showing correspondence between hydration shell density and denature curves within a single protein would be significantly more convincing.
While protein folding and interaction is devilishy tricky to compute, the basic idea that injecting extra energy into a system thats held together only by weak hydrogen bonds will disrupt structure and function hardly requires invocation of additional forms of water.
This isn't to say that the claims may not be true. But I would not jump to "probably".
In fact, your quoted statement doesn't even say that proteins become less stable, what the quoted statement says is that a SINGLE protein (lysozyme) undergoes irreversible structural changes over 65 degrees.
We know of a variety of high temperature resistant proteins (Taq Polymerase for example). While is certainly true that most "ordinary" (ie non extremopile) proteins will probably suffer irreversible structural changes in about that temperature change, it's not super great proof.
It makes me wonder what the pressure dependence is for this phase change. http://www1.lsbu.ac.uk/water/water_phase_diagram.html
Pressures inside a particular piece of cellular machinery can be much higher than 0.1 MPa (1 bar).
If so, there is really no reason to expect this state change to be much affected by pressure.
There also seems to be no latent heat absorbing¹, and from the widely varying changing temperature, I imagine both states coexist on those ~20°C. Water is really weird.
1 - Otherwise people would have discovered this long ago.
> In addition, Raman scattering measurements, obtained using multivariate curve resolution (Raman-MCR) have been used to explore the hydrophobic hydration of linear alcohols from methanol to heptanol [25]. The authors conclude that below 60°C the hydration shells have a hydrophobic-enhanced water structure with a greater tetrahedral order and fewer weak hydrogen bonds than the surrounding bulk water. This configuration disappears above 60°C and is replaced by a structure with weaker bonds. These findings support the existence of two different hydration shells in liquid water with a crossover temperature of ≈60°C.
So it seems that proteins have evolved to stabilize the "ice-like" structure in hydration shells, and in turn depend on those hydration shells to stabilize their 3D structure. Above 50-60°C, that doesn't work. But there are some Archaea that do quite well at 100°C. Their proteins presumably do a better job of stabilizing the "ice-like" structure in hydration shells.
"In conclusion, a review of the physical properties of water in the 0–100°C temperature range reveals a bilinear behaviour that defines a crossover temperature at 50 ± 10°C. This observation supports the hypothesis that there are two states of liquid water. We find that these two states play an important role in the thermal and optical properties of nanomedical systems. Finally, our preliminary findings suggest that the structure of liquid water strongly influences the thermal stability of proteins. More in-depth research on the thermal stability of proteins dispersed in liquid water is needed."
That's covered in the introduction.
> Despite these efforts, the structure of liquid water is still not fully understood.
> This suggests that there are of two states in bulk liquid water that differ in the amount of their dipole moment. Unfortunately, a correlation between the dipole moment and the microscopic structure of these two states has not yet been determined.
Wouldn't weaker hydrogen bounding imply on much lower surface tension?
There is some smaller tension, but the trend is really tiny.
So I don't think that they've found a new phase of water. Rather, as the title states, they argue that liquid water is a mixture of two states, one ice-like with strong hydrogen bonding and tetrahedral structure, and the other more disordered, gas-like, with weaker hydrogen bonding. It's just that there's something like a figure/ground transition at 50-60°C. Going from islands of "gas-like" structure in a sea of "ice-like" structure, to islands of "ice-like" structure in a sea of "gas-like" structure.